Gearboxes are mechanical devices designed to transfer rotational energy from one device to another, such as a rotating wind turbine hub to a generator. They can be found in a variety of applications and industries including wind energy, mining, manufacturing, transportation, etc. Gearboxes heat up and cool down proportionately with the intensity of operation and surrounding environment. Gearboxes heat up and cool down proportionately with the intensity of operation and surrounding environment. The gas (air) inside the cavity's head space, which is the volume in the cavity above the oil level, must be able to expand and contract due to turbulence and these temperature changes without creating any appreciable internal pressure or vacuum respectively. Internal pressure or vacuum may cause the gearbox to leak past the shaft seals in both directions. A seal leak caused by a vacuum condition is of particular concern as this will allow ingestion of contamination directly into the bearing area and entire cavity thereafter. A breather vent is commonly used to allow the gearbox to aspirate freely. As a result of the turbulence and temperature driven aspiration, the gearbox is subject to the continuous ingestion of airborne contamination through a typical breather vent.
Gearboxes are typically deployed in areas that can contain numerous airborne contaminants. Desiccant and other types of filters are typically installed in the breather vent ports as an alternative to a common filterless breather vent. Desiccant breathers are ideal, full aspiration range, short term gearbox filters, but are quickly saturated by ambient humidity rather than the gearbox aspiration itself. As a result, in typical open-air applications, desiccants require continual replacement in order to protect the gearbox. Lastly, once the desiccant media is saturated, they offer no protection against moisture condensates. This leads to a need for more frequent filter maintenance and if not maintained, in the worst case, a catastrophic failure of the gearbox can occur. These repairs are very costly when one considers lost revenue due to down time.
Other solutions include bladder breathers. Bladder breathers are ideal fixed volume, long term, aspiration devises, but typically allow pressure and vacuum gradients to build up, due to bladder stretching, in the gearbox as the pressure or vacuum approaches the check valve limits. They offer no protection in abnormal, harmful, vacuum conditions as they are designed to draw in potentially contaminated make-up air to self-correct the internal and external pressure balance. As a result, they must be designed with substantial volume to cover the full operational range and attempt to cover a portion of the abnormal range.
This improved gearbox isolator differs from other solutions in that it protects the gearbox's entire aspiration range from contamination and in particular, the harmful vacuum conditions that may exist. It accomplishes this with a near zero pressure gradient, safely and compactly, over a significantly extended duration.